The invention relates to drug delivery devices and more particularly to a device for dispensing a controlled amount of a fluid medication.
Medications such as testosterone esters, methotrexate, cyanocobalamin (vitamin B12), dental anesthetics, and botulinum toxin are typically administered as a series of doses of predetermined volume using conventional syringes. For example, botulinum toxin injection is widely used for the treatment of facial wrinkles and consists of a series of injections into specific muscles of the face. Injection of the botulinum toxin into the affected muscles inhibits release of acetylcholine at the neuromuscular junction and causes localized relaxation that smoothes the overlying skin and reduces wrinkles. To ensure that facial asymmetry does not result from uneven dosing of the botulinum toxin, administration of accurate injection volumes is important. This accuracy is conventionally achieved by clinicians through practice to develop consistent technique. Further, and considering the high cost of the botulinum toxin (a typical dose of Botox® Cosmetic consisting of 4 units per 0.1 ml costs a patient on average $40-$60), accurate administration of the botulinum toxin provides financial savings to the clinician as waste is reduced.
Injection devices adapted to deliver a controlled dose of a fluid medication may include electro-mechanical components operable to engage a plunger of a syringe or fluid compartment containing the medication. Such components include drive screws and movable drive elements. Typically these devices are bulky and cumbersome to use.